Incontinence management articles, such as non-cloth disposable diapers, have traditionally utilized absorbent structures which comprise entangled masses of fibers, i.e. non woven fibrous webs. These webs imbibe aqueous fluids, including discharged body fluids, both by an absorption mechanism where fluid is taken up by the fiber material itself, and especially by a wicking mechanism where fluid is acquired by, distributed through and stored in the capillary interstices between the fibers. These webs often comprise loosely compacted, low density layers of absorbent fibers, such as carded cotton webs, air-laid cellulose fibers, comminuted wood pulp fibers, and the like.
Fibrous webs used in such absorbent articles also often include certain absorbent gelling materials usually referred to as "hydrogels," "super absorbent" or "hydrocolloid" materials to store large quantities of the discharged body fluids. See, for example, U.S. Pat. No. 3,699,103 (Harper et al), issued Jun. 13, 1972, and U.S. Pat. No. 3,770,731 (Harmon), issued Jun. 20, 1972, that disclose the use of particulate absorbent gelling materials in absorbent articles. Indeed, the development of thinner diapers has been the direct consequence of thinner absorbent cores that take advantage of the ability of these particulate absorbent gelling materials to absorb large quantities of discharged aqueous body fluids, especially when used in combination with a fibrous matrix. See, for example, U.S. Pat. No. 4,673,402 (Weisman et al), issued Jun. 16, 1987 and U.S. Pat. No. 4,935,022 (Lash et al), issued Jun. 19, 1990, that disclose dual-layer core structures comprising a fibrous matrix and particulate absorbent gelling materials useful in fashioning then, compact, nonbulky diapers.
These particulate absorbent gelling materials are unsurpassed in the market place for their ability to retain large volumes of fluids, such as urine. A representative example of such particulate absorbent gelling materials are lightly crosslinked polyacrylates. Like many of the other absorbent gelling materials, these lightly crosslinked polyacrylates comprise a multiplicity of anionic (charged) carboxyl groups attached to the polymer backbone. It is these charged carboxyl groups that enable the polymer to absorb aqueous body fluids as the result of osmotic forces.
Besides osmotic forces, absorbency based on capillary forces is also important in many absorbent articles, including diapers. Capillary forces are notable in various everyday phenomena, as exemplified by a paper towel soaking up spilled liquids. Capillary absorbents can offer superior performance in terms of the rate of fluid acquisition and wicking, i.e. the ability to move aqueous fluid away from the point of initial contact. Indeed, the dual-layer absorbent core structures of Weisman et al and Lash et al noted above use the fibrous matrix as the primary capillary transport vehicle to move the initially acquired aqueous body fluid throughout the absorbent core so than it can be absorbed and retained by the particulars absorbent gelling material positioned in layers or zones of the core. The fibrous structures disclosed in Weisman et al and Lash et al are produced via air-laying technology. This technology involves air laying the fibers into shaped cavities on a screened drum to form the shape of the core and control the quantity of material used per core. Excess overfill of the shaped cavities is removed and returned to the incoming air stream by a scarfing roll. The Absorbent Gelling Materials (AGM) are added to the airstream along with the fiber materials. This process allows for many alternative shapes to be produced via changes in screen, laydown drum, configuration. Therefore the shape of the material is achieved via "Molding" the fibers into shaped cavities. This process provides shape without trim, which in turn results in minimal scrap.
An alternative absorbent material potentially capable of providing capillary fluid transport would be open-coiled polymeric foams. If made appropriately, open-celled polymeric foams could provide features of capillary fluid acquisition, transport and storage required for use in high performance absorbent cores for absorbent articles such as diapers. Absorbent articles containing such foams could possess desirable wet integrity, could provide suitable fit throughout the entire period the article is worn, and could avoid changes in shape during use. In addition, absorbent articles containing such foam structures could be easier to manufacture on a commercial scale. For example, absorbent diaper cores could simply be stamped out of continuous foam sheets and could be designed to have considerably greater integrity and uniformity than air-laid fibrous absorbent cores containing particulate absorbent gelling materials.
Besides absorbency and manufacturing ease, another potentially desirable property of such foams is the ability to make shaped or contoured absorbent cores having various shape configurations, fluid absorbency properties, etc. Fibrous absorbent cores containing particulate gelling materials have often been shaped or contoured, especially to provide hourglass-shaped configurations. See, for example, the dual-layer absorbent core structures of Weisman et al and Lash et al where the upper layer is in an hourglass-shaped configuration.
Shaped or contoured absorbent cores made from open-celled foam materials having particularly desirable fluid transport characteristics are disclosed in U.S. Pat. No. 5,147,345 (Young et al), issued Sep. 15, 1992. The Young et al absorbent core comprises a fluid acquisition/distribution component that can be fibrous or foam based, as well as fluid storage/redistribution component that comprises a hydrophilic, flexible, open-celled polymeric foam. FIG. 9 of Young et al discloses one such shaped or contoured core having an hourglass-shaped fluid acquisition/distribution layer 73 comprising a fibrous absorbent material overlying an hourglass-shaped fluid redistribution/storage layer comprising an open-cell absorbent foam. See also FIG. 2 which discloses a smaller rectangular fluid acquisition/distribution layer 51 comprising a fibrous absorbent material overlying a larger hourglass-shaped fluid redistribution/storage layer 52 comprising an open-celled polymeric foam.
Forming shaped or contoured absorbent cores or layers from foam materials, including those disclosed in Young et al, is not without problems. The hourglass-shaped foam layer shown in FIGS. 9 and 2 of Young et al is typically made from a single rectangular piece of foam. This rectangular piece of foam can be notched, cut or otherwise severed to form the hourglass-shaped piece. In carrying out these operations, a significant amount of unusable foam scrap can be created. Indeed, it has been found that, in forming hourglass-shaped foam pieces, as much as 15 to 25% of the total foam material used can end up as unusable scrap.
In addition, unitary hourglass-shaped foam pieces can create certain problems in terms of comfort of the absorbent article in which the absorbent foam core is used. In the case of higher modulus absorbent foams, hourglass-shaped unitary cores can be less soft and less flexible. This is especially true in the crotch area of an absorbent core made from a unitary hourglass-shaped absorbent foam layer. Accordingly, it would be desirable to be able to make shaped or contoured absorbent cores from polymeric foams that: (1) reduce generation of foam scrap; and (2) provide greater softness and flexibility, especially in the crotch area.
Previous product designs for shaped absorbent core structures generated from rectilinear roll stock, web, materials have generally produced significant amounts of scrap which must be discarded or recycled during the manufacturing process. Designs which utilize multiple rolls of various width material to generate shape are sometimes difficult to execute, specifically when they utilize very narrow webs of material. Large rolls of narrow webs are very difficult to manufacture and equally difficult to process into absorbent articles.
Attempts have been made previously to reduce the amount of scrap material produced during the manufacture of patterned articles derived from a continuous web. For example, each of U.S. Pat. No. 4,760,764 to Jonckheere et al. and EP 0539 032 A1 to Johnson & Johnson describe a manufacturing method with a reduced amount of waste material in which a continuous web of material is continuously cut in a cyclic pattern to provide two strips, each having a patterned longitudinal edge and a straight edge. The strips are cross directionally displaced, phased such that the tabs are aligned and then joined together in an overlapping fashion to form a two layered central region producing the edge contour of the final disposable absorbent product. Such products are limited to a single design structure having only two layers in the central region with only a single layer in the ear or tabular areas. Although this pattern could be repeated again on top of itself, the number of layers in the central region will be twice that of the layers that are present in the outer shaped regions. Such an arrangement although potentially effective from a fluid absorption standpoint, is less desirable from a stiffness, flexibility, overall thickness and crotch bulk minimization standpoint.
U.S. Pat. No. 3,072,123 (Davis), Jan. 8, 1963, shows a plurality of adjacent wave-like cutting lines forming nested shapes which are then further processed to form an absorbent article. Since this application is essentially intended to produce a unitary structure from the nested shapes, the outermost, partial, shapes provide no usefulness and therefore result in scrap material. This approach is unlike that of the present which utilizes the partial shaped segments as well as the full shapes, therefore resulting in essentially "Zero scrap." U.S. Pat. No. 3,878,286 (Jones), Apr. 15, 1975 is intended to produce a nested absorbent structure, however, as in U.S. Pat. No. 3,072,123, the outermost areas of the web which contain only partial structures or shapes, lacks usefulness and therefore results in scrap material. U.S. Pat. No. 4,862,574 (Seidy), Sep. 5, 1989, illustrates a method of producing a panty protector. Although this application does show a repeating cutting pattern or wave type pattern, the pattern is cross direction and not continuous in the machine or web, direction. Therefore, the approach of U.S. Pat. No. 4,862,574, produces discrete components versus the intent of the present invention which is to produce a continuous pattern resulting in multiple webs of product shapes in a continuous web. The cutting pattern incorporated in U.S. Pat. No. 4,862,574 results in partial structures which, as in the previously noted patents, provide no usefulness with respect to their respective inventions. U.S. Pat No. 3,527,221 (Croon et al), Sep. 8, 1970, shows a wave-like cutting pattern utilized to shape the outer covering, chassis, of a diaper. Although this approach results in minimal scrap, it is not applied to the absorbent structure itself and it also involves no layering of the separated structures as in the present invention.
U.S. Pat Nos. 5,102,487; 5,034,007; 4,595,441 and 5,330,598 describe continuous strips of materials in conjunction with repeating patterns none of these inventions are intended to provide absorbent core structures. Also, none of the aforementioned patents involve more than two strips of material as does the present invention.
Furthermore, none of prior art references teach the manufacture of an absorbent core structure having a plurality of layers of absorbent material in the crotch area and the "ear" or tabular region, wherein the absorbent core structure is formed from a single web, while eliminating scrap formation.
It is, therefore, a major object of the present invention to provide a manufacturing method for producing an absorbent core material from a single web of material so that there is "zero scrap".
It is another object of the present invention to provide a manufacturing method for producing an absorbent structure having at least two layers of an absorbent core material in both the crotch area and the "ear" portions of the absorbent structure in which the core structure is formed from a single web of absorbent material.
It is another object of the present invention to provide a manufacturing method for producing a variety of absorbent core structures from a single web of absorbent material having different configurations depending upon the desired use of such absorbent cores.
It is still another object of the present invention to provide an absorbent core structure having improved absorbent efficiency and greater softness and flexibility for use in the production of diapers, incontinent products, etc.